Stop #defining FREEBSD_ELF

This was originally used (along with FREEBSD_AOUT) to prefer the use
of ELF in various tools instead of a.out as part of the a.out to ELF
transition in the 3.x days.  The last use of it was removed from
<link.h> in commit 66422f5b7a back in
2002, but various files still #define it.

Reviewed by:	kevans, imp, emaste
Sponsored by:	DARPA
Differential Revision:	https://reviews.freebsd.org/D42964

(cherry picked from commit 4a3cf5f329)

libexec/rtld-elf/Makefile

@@ -38,7 +38,7 @@ SRCS= \
 	libmap.c
 MAN?=		rtld.1
 ACFLAGS+=	-DLOCORE
-CFLAGS+=	-Wall -DFREEBSD_ELF -DIN_RTLD -ffreestanding
+CFLAGS+=	-Wall -DIN_RTLD -ffreestanding
 CFLAGS+=	-I${SRCTOP}/lib/csu/common
 .if exists(${RTLD_ELF_DIR}/${MACHINE_ARCH:S/powerpc64le/powerpc64/})
 RTLD_ARCH=	${MACHINE_ARCH:S/powerpc64le/powerpc64/}

stand/common/load_elf.c

@@ -35,7 +35,6 @@
 #include <string.h>
 #include <machine/elf.h>
 #include <stand.h>
-#define FREEBSD_ELF
 #include <sys/link_elf.h>
 
 #include "bootstrap.h"

stand/common/load_elf_obj.c

@@ -35,7 +35,6 @@
 #include <string.h>
 #include <machine/elf.h>
 #include <stand.h>
-#define FREEBSD_ELF
 #include <sys/link_elf.h>
 
 #include "bootstrap.h"

stand/common/reloc_elf.c

@@ -33,7 +33,6 @@
 
 #include <stand.h>
 
-#define FREEBSD_ELF
 #include <sys/link_elf.h>
 
 #include "bootstrap.h"

usr.sbin/kldxref/ef.c

@@ -43,7 +43,6 @@
 #include <string.h>
 #include <unistd.h>
 #include <machine/elf.h>
-#define FREEBSD_ELF
 
 #include "ef.h"
 

usr.sbin/kldxref/ef_obj.c

@@ -45,7 +45,6 @@
 #include <string.h>
 #include <unistd.h>
 #include <machine/elf.h>
-#define FREEBSD_ELF
 
 #include "ef.h"
 

usr.sbin/kldxref/kldxref.c

@@ -42,7 +42,6 @@
 #include <sys/linker.h>
 #include <sys/stat.h>
 #include <sys/module.h>
-#define FREEBSD_ELF
 
 #include <ctype.h>
 #include <err.h>